An Agent Based Transaction Manager for Multidatabase Systems

A multidatabase system (MDBMS) is a facility that allows users to access data located in multiple autonomous database management systems (DBMSs) at different sites. To ensure global atomicity for multidatabase transactions, a reliable global atomic commitment protocol is a possible solution. In this protocol a centralized transaction manager (TM) receives global transactions, submits subtransactions to the appropriate sites via AGENTS. An AGENT is a component of MDBS that runs on each site; AGENTS after receiving subtransactions from the transaction manager perform the transaction and send the results back to TM. We have presented a unique proof-of-concept, a JAVA application for an Agent Based Transaction Manager that preserves global atomicity. It provides a user friendly interface through which reliable atomic commitment protocol for global transaction execution in multidatabase environment can be visualized. We demonstrated with three different test case scenarios how the protocol works. This is useful in further research in this area where atomicity of transactions can be verified for protocol correctness

Poster session: Constrained dynamic physical database design

Physical design has always been an important part of database administration. Today's commercial database management systems offer physical design tools, which recommend a physical design for a given workload. However, these tools work only with static workloads and ignore the fact that workloads, and physical designs, may change over time. Research has now begun to focus on dynamic physical design, which can account for time-varying workloads. In this paper, we consider a dynamic but constrained approach to physical design. The goal is to recommend dynamic physical designs that reflect major workload trends but that are not tailored too closely to the details of the input workloads. To achieve this, we constrain the number of changes that are permitted in the recommended design. In this paper we present our definition of the constrained dynamic physical design problem and discuss several techniques for solving it

Pinwheel Scheduling for Fault-tolerant Broadcast Disks in Real-time Database Systems

The design of programs for broadcast disks which incorporate real-time and fault-tolerance requirements is considered. A generalized model for real-time fault-tolerant broadcast disks is defined. It is shown that designing programs for broadcast disks specified in this model is closely related to the scheduling of pinwheel task systems. Some new results in pinwheel scheduling theory are derived, which facilitate the efficient generation of real-time fault-tolerant broadcast disk programs.National Science Foundation (CCR-9308344, CCR-9596282

Lenguajes y modelos subyacentes a los grafos de conocimiento

A knowledge graph is a large database that integrates information from different data sources, this with the objective of supporting knowledge extraction, and allowing the transformation of such knowledge into value for the users. Such database is represented as a graph where the nodes represent entities, and each edge represents a relationship between nodes, or the attribute of a node. The objective of this article is to review the data models used to represent knowledge graphs, and the query languages that allow to extract explicit and implicit information contained in such graphs.Un grafo de conocimiento es una gran base de datos que integra información desde distintas fuentes de datos, esto con el objetivo de poder extraer conocimiento y transformarlo en valor para los usuarios. Dicha base de datos es representada como un grafo donde los nodos representan entidades, y cada arista representa una relación entre dos nodos, o un atributo de un nodo. El objetivo de este artículo es presentar una revisión de los modelos de datos que se usan para representar grafos de conocimiento, y los lenguajes de consulta que permiten extraer la información explícita e implícita contenida en dichos grafos